The effects of vaporisation, condensation and diffusion of water inside the tissue during saline-infused radiofrequency ablation of the liver: A computational study

Abstract

Saline-infused radiofrequency ablation (RFA) is a thermal ablation technique that combines saline infusion and Joule heating to destroy cancer tissues. During treatment, the intense heat generated can cause water from the infused saline and inside the tissue to vaporise. Conventionally, the effects of vaporisation have been modelled by adopting the apparent heat capacity method. However, this approach does not account for the loss of water content during vaporisation, which raises questions on its accuracy, primarily because of the large water content present during saline-infused RFA. To address this, the present study proposes an alternative approach to model vaporisation effects during saline-infused RFA. The approach adopts and modifies the water fraction method to account for the effects of vaporisation, condensation and diffusion of water inside the tissue during saline-infused RFA. The framework was compared against the commonly used apparent heat capacity method through numerical simulations carried out on 3D finite element models of the liver. Results indicated that unlike condensation, the role of diffusion of water during saline-infused RFA was not as significant as condensation, where the latter was found to affect the ablation process. With the water fraction method, there was a trend of exponential decrease in tissue electrical conductivity with time, which ultimately led to the prediction of smaller coagulation volume than that of the apparent heat capacity method.